Mobile telematics is a rapidly advancing technology, as more and more users want to be able to gain access and use applications while on the move. For example, IEEE 802.11b wireless LAN, operating at 11 Mb/s, and IEEE 802.11a, operating at 54 Mb/s, have received considerable market acceptance and have proliferated in private and public space. New laptops, notebook computers, and PDA are beginning to have embedded IEEE 802.11 LAN cards and wireless access points may become as ubiquitous as telephone jacks. 3G mobile wireless data service is an emerging technology and WLAN having relatively high-bandwidth capability and low, equipment cost (no spectrum license fee) is being considered as either a competitor or complementary to 3G mobile wireless data service.
However, in order to be useful in the mobile environment, fast handoff between access points belonging to different networks is required. There are several components that contribute to overall handoff delay in a mobile environment. For example, as the mobile user moves from one coverage area to another, a decision must be made whether to connect to a different access point which may result in layer 2 detection delays. Layer 2 detection delays have been largely overcome in some technologies, such as CDMA, that provide soft handoff techniques and beacon interval from an access point will generally account for the delay caused by layer 2 detection. In general, a measure of good performance with respect to level 2 delays is about 100 ms.
Once the layer 2 handoff is complete, the mobile device must determine that it is in a different subnet. This is generally achieved by listening to advertisements from an ICMP router, a foreign agent (FA), or other server. During this process the mobile device must reconfigure itself with a new IP address or foreign agent care-of-address (COA). This also contributes to overall handoff delay and is characterized as IP address discovery phase.
Following reconfiguration of the mobile device and new IP address assignment, further delays can occur, generally characterized as media redirection delays. In particular, depending on the mobility management scheme being used, the mobile device will send a SIP Re-invite, MIP register or MIP update message so that the media will get redirected to the new IP address. Redirection delays can vary depending on the number of signaling messages needed, and the distance between the mobile device and the correspondent host.
While the prior art has considered a variety of ways of reducing overall handoff delay by treating the various components that contribute to the handoff delay, there remains a need in the art for improvements in this area.